G-SYNC 101: G-SYNC vs. V-SYNC OFF

Beyond the Limits of the Scanout

It’s already been established that single, tear-free frame delivery is limited by the scanout, and V-SYNC OFF can defeat it by allowing more than one frame scan per scanout. That said, how much of an input lag advantage can be had over G-SYNC, and how high must the framerate be sustained above the refresh rate to diminish tearing artifacts and justify the difference?

Quite high. Counting first on-screen reactions, V-SYNC OFF already has a slight input lag advantage (up to a 1/2 frame) over G-SYNC at the same framerate, especially the lower the refresh rate, but it actually takes a considerable increase in framerate above the given refresh rate to widen the gap to significant levels. And while the reductions may look significant in bar chart form, even with framerates in excess of 3x the refresh rate, and when measured at middle screen (crosshair-level) only, V-SYNC OFF actually has a limited advantage over G-SYNC in practice, and most of it is in areas that one could argue, for the average player, are comparatively useless when something such as a viewmodel’s wrist is updated 1-3ms faster with V-SYNC OFF.

This is where the refresh rate/sustained framerate ratio factors in:

As shown in the above diagrams, the true advantage comes when V-SYNC OFF can allow not just two, but multiple frame scans in a single scanout. Unlike syncing solutions, with V-SYNC OFF, the frametime is not paced to the scanout, and a frame will begin scanning in as soon as it’s rendered, regardless whether the previous frame scan is still in progress. At 144Hz with 1000 FPS, for instance, this means with a sustained frametime of 1ms, the display updates nearly 7 times in a single scanout.

In fact, at 240Hz, first on-screen reactions became so fast at 1000 FPS and 0 FPS, that the inherit delay in my mouse and display became the bottleneck for minimum measurements.

So, for competitive players, V-SYNC OFF still reigns supreme in the input lag realm, especially if sustained framerates can exceed the refresh rate by 5x or more. However, while at higher refresh rates, visible tearing artifacts are all but eliminated at these ratios, it can instead manifest as microstutter, and thus, even at its best, V-SYNC OFF still can’t match the consistency of G-SYNC frame delivery.

Should “Reduce Buffering” option in Overwatch be enabled or disabled? Many competitive/pro players suggest having reduce buffering on to get higher framerate and reduced input lag but would having this option on have a negative effect on G-SYNC?

Also I recently upgraded my system to a i7-8700k and 1080ti. I usually sit at a steady 300fps on Overwatch now and use a 240hz monitor (Asus PG258Q). Would G-SYNC be worth using in this case?

“Reduced Buffering” is effectively Overwatch’s version of Nvidia’s “Maximum pre-rendered frames” set to “1,” so yes, leave it enabled for the lowest input lag, and no, it does not interfere with G-SYNC functionality; it was enabled for all the tests in this article. As for 240Hz G-SYNC w/238 or 237 FPS limit vs. 240Hz V-SYNC OFF w/238 or 237 FPS limit, the lag difference is almost zero; see the 240Hz chart on this page here. And for 240Hz G-SYNC w/238 or 237 FPS limit vs. 240Hz V-SYNC OFF at 300 FPS, you’re only looking at a 1ms difference in lag,… Read more »

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5 months 18 days ago

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pervyjutsu

So I’ve been experimenting with the different kinds of settings: – 240Hz G-SYNC w/ 238 or 237 FPS limit – 240Hz V-SYNC OFF w/ 238 or 237 FPS LIMIT – 240Hz V-SYNC OFF w/ 300 FPS limit I actually found myself liking 240Hz V-SYNC OFF w/ 238 or 237 FPS LIMIT the best. Up until now I have always used 300 FPS limit because that is what everyone said was best input lag-wise, but after trying the lower 238 or 237 limit today, wow I can aim so much better for some reason? It is definitely not placebo because I… Read more »

We always have to consider the (never to be underestimated) placebo effect, but… Like I mentioned in my last reply, the unique way each of those various scenarios deliver frames could be causing subtle differences in lag patterns that may affect aiming; muscle memory, conditioning, subconscious processes, etc. Because quite frankly, unless Overwatch is doing something abnormal with a 300 FPS limit above your refresh rate (which none of my existing tests show), or you’re experiencing a system specific issue, then the scenario you’re claiming feels more responsive, is actually slightly less responsive, at least where raw average input lag… Read more »

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5 months 17 days ago

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bcbuse

First, this is the best Gsync/Vsync information on the internet. I appreciate the effort you put into this, well done.

I read a comment you posted somewhere that ‘technically’ the absolute least input lag would be with Gsync Off + Vsync Off + Framerate upcapped(getting at least 2x the monitor refresh rate). Can you approximate how much less input lag that would be versus Gsync On + Vsync On(NVCP) + Framerate capped 2 below monitor refresh rate?

Depends on the maximum refresh rate and how high the framerate is sustained above it, but at 2x ratio, and at higher refresh rates, you’re looking at only 1-3ms less average input lag with G-SYNC off + V-SYNC off + FPS uncapped vs. G-SYNC on + V-SYNC on + -2 FPS limit when measured at crosshair level.

You can see the worst case first reaction differences between those two scenarios on the ninth page here.

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5 months 19 days ago

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daniel8747

to clarify: with fps capped 2-3 fps below monitor refresh rate, do i still need to have v-sync enabled?

Sort the comments here by newest; the answer is in the reply to the comment below yours, as well as in the “Range” section of this article.

Short answer to your question is “yes,” but only if you never want to see tearing.

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15 hours 33 minutes ago

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SturmButcher

I don’t understand something…. Why do I need V-Sync on with G-Sync?, The last one already sync frames and If I use a frame limiter I would never need V-Sync, I don’t understand guys. I am suspecting that G-Sync+V-Sync+RTSS is causing stutter in some games…Could you please enlighten me?

I’ve explained this ad nauseam (including in this article), but I’ll try to break it down as clearly as possible yet again… Within the G-SYNC range (e.g. within the refresh rate), G-SYNC is V-SYNC, and V-SYNC is G-SYNC. The “V-SYNC” option in the “on” position with G-SYNC enabled was originally a non-optional part of G-SYNC. It was only at a later point Nvidia revealed the V-SYNC “on/off” option in the control panel so that the screen would tear with V-SYNC “off” when the framerate exceeded the G-SYNC range/refresh rate, instead of reverting to V-SYNC behavior. However, the V-SYNC option also… Read more »

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16 days 4 hours ago

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vityapapa

The Csgo input-lagg is the best g-sync off+v-sync off and fps_max 0? i have 144hz monitor.